1. Field of the Invention
This invention relates to a process for the uniform sulfonation of elastomeric or thermoplastic polymers. More particularly, this invention is directed to a process for the preparation of sulfonated elastomeric or thermoplastic polymers from hydrocarbon polymers characterized before sulfonation by the presence in said polymers of sulfonatable sites selected from the group consisting of: olefinic unsaturation, which may be located in the polymer backbone chain of carbon atoms or in acyclic or alicyclic hydrocarbon groups pendant to the polymer backbone chain and arylene groups pendant to the polymer backbone chain of carbon atoms in which said backbone chain may be saturated, contain olefinic unsaturation and have appended to it unsaturated acyclic and alicyclic groups.
Most particularly, this invention is directed to a process for the bulk sulfonation of said unsaturated and aromatic ring containing polymers and mixtures of hydrocarbon polymers including said polymers which include:
(A) MECHANICALLY MIXING, AT AN INTENSITY WHICH CAN VARY FROM SIMPLY KNEADING OR MASTICATION TO A HIGH DEGREE OF SHEAR, ONE OR MORE OF THE POLYMERS, OR A MIXTURE OF HYDROCARBON POLYMERS INCLUDING THE POLYMERS WITH A SULFONATION REAGENT INCLUDING SULFURIC ACID OR SULFUR TRIOXIDE, IN THE SUBSTANTIAL ABSENCE OF A SOLVENT FOR THE POLYMERS, AT A TEMPERATURE WHICH IS HIGHER THAN THE GLASS TRANSITION TEMPERATURE (Tg) of the polymers or mixture of polymers including the polymers in the case of amorphous polymers and is higher than the crystalline melt temperature (Tm) of the polymer or mixtures of polymers which are crystalline for a time sufficient to effect the desired degree of sulfonation; followed by
(B) RECOVERY OF THE FREE SULFONIC ACID OF THE POLYMER; OR
(C) NEUTRALIZATION WITH A BASIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF AMMONIA, MONOALKYL AND POLYALKYLENE AMINES, THE COMPOUNDS IN WHICH THE CATION IS AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF Groups I-A, I-B, II-A and II-B of the Periodic Table of Elements, aluminum, antimony and lead; and the anion is selected from the group consisting of oxides, hydroxides, C.sub.1 to C.sub.5 alkoxides, carbonates, and carboxylic acids.
Sulfonated polymers made by the process of this invention when neutralized with monovalent and polyvalent cations can yield ionically cross-linked products which are elastomeric at ambient temperatures but are thermoplastic at elevated temperatures permitting the products to be extruded, blow molded, injection molded, sheeted and vacuum formed. Sulfonated polymers such as polystyrene, for example, yield on neutralization with alkalies, lower amines and the like, products useful as thickening agents as rigid foams and plastic-like applications. Sulfonated elastomers having 10 mole percent or less, preferably 0.2 to 5.0 mole percent of sulfonic acid groups incorporated therein, when ionically cross-linked or neutralized, may be blended with other polymers which may be amorphous or crystalline to yield compositions having novel physical properties.
2. Prior Art
Sulfonated polymers, varying in utility from water-soluble resins to ionically cross-linked thermoplastic elastomers are old in the art but virtually all processes described in patents and the chemical literature utilize a solvent for the polymer or synthesize the polymer from monomers possessing a sulfonic acid group. Exceptions involve surface sulfonation of covalently cross-linked polymers lacking thermoplastic or elastomeric properties. Examples of these processes include:
U.S. Pat. No. 2,533,210 describes the preparation of a water-soluble sulfonated polystyrene by sulfonating a polymer of styrene dissolved in a chlorinated solvent with a complex of SO.sub.3 and bis (.beta.-chloroethyl) ether.
U.S. Pat. No. 3,322,734 discloses the preparation of plastic polymers containing ionic cross-links by the copolymerization of styrene sulfonic acid with other monomers.
Vinyl sulfonic acid readily forms water-soluble homopolymers and copolymers with a variety of polar monomers but with the exception of styrene (Kern et al; Makromol. Chem. 32, 37 (1959)) attempts to copolymerize this monomer with hydrocarbon monomers, e.g. isobutylene and butadiene, failed. See Breslow et al, J. Poly. Sct. 27, 295 (1958).
The preparation of water-soluble sulfonic acids of natural rubber by reaction of a rubber cement with oleum or chlorosulfonic acid complexed with an ether or ester is described in German Pat. Nos. 550,243; 572,980; 582,565; and 585,623.
U.S. Pat. No. 3,218,301 discloses the sulfonation of a cross-linked vinyl polymer in the absence of solvent by passing gaseous SO.sub.3 upwardly through a reactor containing particles of the polymer having a macroreticular structure and a size in the micron range at rate sufficient to fluidize the reactor contents.
British Patent No. 1,100,712 describes the production of an antistatic surface treatment for polystyrene articles using a bath of an aliphatic hydrocarbon and chlorosulfonic acid.
Recently, U.S. Pat. Nos. 3,072,618; 3,642,728; and 3,836,511, which are herein incorporated by reference, have disclosed the preparation of novel sulfonic acid ionomers of unsaturated elastomers by reaction of the polymers in solution with a variety of organic complexes of sulfuric acid and sulfur trioxide.